1. Field of the Invention
The present invention relates to a day display apparatus and a watch having the same.
2. Description of the Related Art
In watches, a day display apparatus configured to be able to display the date with large figures by rotating a second day display wheel which is jumped and stopped in rotation by a second day display wheel jumper and displays the date in the tens place every time when a first day display wheel which displays the date in the ones place reaches a predetermined rotational position, that is, a rotational position where the displayed date changes from 9 to 0 (that is, rotational positions where the date changes from 09 to 10, 19 to 20, and 29 to 30) or a rotational position where the displayed date changes from 31 to 01 by a program tooth portion is known (Patent Document JP-A-2005-214837, Patent Document JP-T-2006-522323).
In the display apparatus in Patent Document JP-A-2005-214837, the first day display wheel and the second day display wheel have gear portions positioned so as to oppose to each other in the radial direction with the intermediary of an annular area, and the program tooth portion of the first day display wheel is engaged with the gear portion of the second day display wheel via a day intermediate wheel positioned in the annular area. Therefore, in the display apparatus in Patent Document JP-A-2005-214837, when the program tooth portion is at a rotational position which does not allow the engagement with the day intermediate wheel, there is no member which controls the rotational position of the second day display wheel other than the second day display wheel jumper, so that there is a risk of occurrence of a date hopping when the restraint of the second day display wheel by the second day display wheel jumper is temporarily released by an impact due to a drop or the like and hence the second day display wheel is rotated.
In contrast, Patent Document JP-T-2006-522323 proposes a technology in which pins which are both positioned along the circumference and are able to enter into and exit from depressed portions of a wheel of an intermediate gear train which connects the first and second day display wheels are provided to increase the resistance of the wheel against the rotation so that the day display wheel is avoided from excessively rotating when the date is changed by manual rotation or the like and being displaced from the date position which should be normally displayed.
However, with the technology disclosed in Patent Document JP-T-2006-522323 as well, the restraint of the second day display wheel by the second day display wheel jumper is temporarily released due to the impact such as the drop and hence the second day display wheel is rotated, so that the risk of occurrence of the date hopping cannot be avoided reliably.
When the date hopping occurs as described above, the wrong date which is different from the date to be displayed is undesirably displayed.